August 30, 2012

Commenters here have pointed out a stunning feature made clear at the University of Bremen Sea Ice page. With a little searching I found an animation that makes it even clearer.

The image above covers the last 30 days of melting. At the 5 second mark, you can see an enormous blob break free in the Chukchi Sea area, fly apart and disappear in the anomalously warm ocean water.

In the last few frames another huge mass in the central arctic seems about to pull away and dissolve in a similar process. I’m learning to read these images along with everyone else, but it would seem that whether it eventually melts or freezes in place is dependent on how much longer this process continues.

August 29, 2012

“Am I wrong to infer a relationship between degree of minimum extent and timing of minima? It seems that larger ice volumes hit their minimum earlier in the year. Could we thus expect this year’s ice extent minimum to be later still, perhaps even into October?”

No way I’m going to go out on a limb here. We are thru the looking glass at this point, but just eyeballing the graph (always dangerous) – it would seem not out of the question.
Experts – I know you’re out there – feel free to weigh in.

August 29, 2012

One of the confusing issues that newbies run into is the distinction between the various measures of arctic ice, including “area” vs “extent”. NSIDC addresses this in a FAQ.

What is the difference between sea ice area and extent?

Area and extent are different measures and give scientists slightly different information. Some organizations, including Cryosphere Today, report ice area; NSIDC primarily reports ice extent. Extent is always a larger number than area, and there are pros and cons associated with each method.

A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. A more precise explanation of extent versus area gets more complicated.

Extent defines a region as “ice-covered” or “not ice-covered.” For each satellite data cell, the cell is said to either have ice or to have no ice, based on a threshold. The most common threshold (and the one NSIDC uses) is 15 percent, meaning that if the data cell has greater than 15 percent ice concentration, the cell is considered ice covered; less than that and it is said to be ice free. Example: Let’s say you have three 25 kilometer (km) x 25 km (16 miles x 16 miles) grid cells covered by 16% ice, 2% ice, and 90% ice. Two of the three cells would be considered “ice covered,” or 100% ice. Multiply the grid cell area by 100% sea ice and you would get a total extent of 1,250 square km (482 square miles).

Area takes the percentages of sea ice within data cells and adds them up to report how much of the Arctic is covered by ice; area typically uses a threshold of 15%. So in the same example, with three 25 km x 25 km (16 miles x 16 miles) grid cells of 16% ice, 2% ice, and 90% ice, multiply the grid cell areas that are over the 15% threshold by the percent of sea ice in those grid cells, and add it up. You would have a total area of 662 square km (255.8 square miles).

Scientists at NSIDC report extent because they are cautious about summertime values of ice concentration and area taken from satellite sensors. To the sensor, surface melt appears to be open water rather than water on top of sea ice. So, while reliable for measuring area most of the year, the microwave sensor is prone to underestimating the actual ice concentration and area when the surface is melting. To account for that potential inaccuracy, NSIDC scientists rely primarily on extent when analyzing melt-season conditions and reporting them to the public. That said, analyzing ice area is still quite valuable. Given the right circumstances, background knowledge, and scientific information on current conditions, it can provide an excellent sense of how much ice there really is “on the ground.”

August 29, 2012

Regular readers and viewers will have seen all of these, – so apologies to those – but at this moment, with many more viewers paying attention, there is no substitute for repetition.
We are all flooded with a sea of information, and the mission of this series is to provide context and narrative, especially at moments of critical interest.

This is from the Yale Series, “This is Not Cool”, a companion to the Climate Crocks series.

Here are the Climate Crocks Sea ice videos from the last 2 years. Again, apologies, but I invite new viewers to check these still-very-informative videos out for background.

August 29, 2012

The graph shows IPCC model runs projecting arctic sea ice loss into the future. The red is actual observations. Far from being “alarmist”, the IPCC has actually been far to conservative on this issue, leaving scientists scrambling to catch up with reality.Source: Stroeve et al, NSIDC

Over the past three decades, the summer Arctic sea ice extent has declined roughly 40 percent, and the ice has lost significant volume, according to data from the Polar Science Center. Mark Serreze, director of the National Snow and Ice Data Center, told the Guardianlast year: “The extent is going down, but it is also thinning… There will be ups and downs, but we are on track to see an ice-free summer by 2030.”

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A new study in this month’s Environmental Research Letters concludes that between 70 and 95 percent of the Arctic melt since 1979 has been caused by human activity. Man-made global warming has rapidly heated up the Arctic — the region has been warming about twice as fast as the global average. (See here for a good explanation of why.) What’s more, soot and other pollutants from smokestacks in Europe and Asia have traveled up to the Arctic. When those dark particles settle onto the snow and ice, they absorb sunlight and start sizzling.

Natural variability still plays a small role, however. This year, a large storm in August may have helped break up the sea ice and caused it to melt even more quickly. But NSIDC scientists say the long-term warming trend was the main driver — the slushy ice has become even more vulnerable to weather outbursts.

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In the past, scientists have underestimated the pace at which Arctic sea ice would disappear. In 2007, the Intergovernmental Panel on Climate Change (IPCC) figured we wouldn’t see ice-free summers in the Arctic until the end of the century or so. But later observations suggested that sea-ice extent is shrinking far more quickly than the IPCC had forecast.

It appears that earlier climate models underestimated certain “feedback” effects. As Arctic sea ice melts, more and more of the ocean is exposed to sunlight. Since the darker ocean surface absorbs more sunlight than the bright ice, this warms the region even further. What’s more, a recent study in the Journal of Geophysical Letters found that IPCC models had low-balled the rate at which melted ice drifts off, further accelerating the collapse. That explains why some scientists have revised their forecasts, saying ice-free summers could come 40 or 50 years ahead of schedule.

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Melting Arctic sea ice won’t, by itself, raise global ocean levels. But a warmer Arctic will cause Greenland’s ice sheet to melt — and that matters. Ice that’s floating in the ocean can’t raise sea levels when it melts, because the ice was already displacing its own volume. But as the exposed ocean absorbs more sunlight, the region will keep heating up. And that’s important when it comes to the vast ice sheet covering Greenland.

Greenland’s ice sheet is 1.9 miles thick and contains enough ice to raise global sea levels by about 25 feet (7.5 meters) all told. Back in 2007, the IPCC consensus was that Greenland’s ice sheet would remain fairly stable this century and wouldn’t contribute much to sea level rise. But more recent evidence suggests that this prediction is out of date. The melting of Greenland’s ice sheet appears to be accelerating of late, losing about four times as much mass last year as it did a decade ago. That’s partly due to warmer air. And it’s partly driven by rising ocean temperatures, as warmer water chews away at the edges of the ice sheet.

As a result, a recent study by the U.S. Jet Propulsion Laboratory predicted that sea levels are on pace to rise at least a foot by 2050, and possibly three feet by century’s end. (Longer-term forecasts depend on how rapidly Antarctica’s own massive ice sheets deteriorate.)

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The changing Arctic could lead to more extreme summers and winters in the United States and Europe. It’s no shock that global warming will make summers even hotter. But could it also make winters colder? Perhaps. For that, we can thank the Arctic. As Jennifer Francis, a climate scientist at Rutgers, has been exploring, the amplified warming in the Arctic might well be contributing to extreme weather.

Why is that? First, the west-to-east jet stream appears to be slowing down, which allows weather patterns to persist in certain areas for longer. This could help account for the onslaught of snowstorms in the United States and Europe in 2009 and 2010, as well as prolonged heat waves like the one that hit Moscow in 2010. Arctic amplification can also increase the “waviness” of the jet stream surrounding the polar region. That could allow more frequent blasts of cold Arctic air to escape down into North America or Europe, leading to frigid winters.

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The Arctic hasn’t yet reached the “point of no return,” but the world would have to cut emissions very quickly to stabilize the sea ice. One 2010 study in Nature found that it was still possible to halt the shrinking of Arctic sea ice. A more recentstudy in Science, looking at 10,000 years of Arctic melt, also concluded that we’re not yet at a “tipping point,” where the collapse in sea ice becomes inevitable. “The good news,” said Sven Funder, a co-author of the Science study, “is that even with a reduction to less than 50% of the current amount of sea ice the ice will not reach a point of no return.”

And yet, as climate blogger Joe Romm explained after the Nature study came out, we may have reached a practical point of no return. The Nature authors estimated that the world would have to cut greenhouse-gas emissions by 60 percent rapidly and keep cutting thereafter to avert the inexorable collapse of summer sea-ice. That’s unlikely. A (shrinking) number of climate scientists still think the world can cut emissions significantly and avert a 2°C rise in temperature. Yet the prognosis for Arctic sea ice looks a bit grimmer.

August 28, 2012

The amount of sea ice in the Arctic has fallen to the lowest level on record, a confirmation of the drastic warming in the region and a likely harbinger of larger changes to come.

Satellites tracking the extent of the sea ice found over the weekend that it covered about 1.58 million square miles, or less than 30 percent of the Arctic Ocean’s surface, scientists said. That is only slightly below the previous record low, set in 2007, but with weeks still to go in the summer melting season, it is clear that the record will be beaten by a wide margin.

According to research by the National Snow and Ice Data Center (NSIDC), based at the University of Colorado at Boulder, the decline in summer Arctic sea ice “is considered a strong signal of long-term climate warming”.

Arctic sea ice fell to 4.10 million square kilometres, some 70,000 square kilometres less than the earlier record charted on September 18, 2007, says the NSIDC.

Scientists say the record was all the more striking as 2007 had near perfect climate patterns for melting ice, but that the weather this year was unremarkable other than a storm in early August.

“I think, unfortunately, this is an example that points more to the worst-case scenario side of things,” says Professor Michael E. Mann, of Penn State University, who was a lead author of a major UN report in 2001 on climate change.

“There are a number of areas where in fact climate change seems to be proceeding faster and with a greater magnitude than what the models predicted.”

The Arctic region is now losing about 155,000 square kilometres (60,000 square miles) of ice annually, the equivalent of a US state every two years, said Walt Meier, a scientist at the National Snow and Ice Data Center.

“It used to be the Arctic ice cover was a kind of big block of ice. It would melt a little bit from the edges but it was pretty solid,” Meier told reporters on a conference call.

“Now it’s like crushed ice,” he said. “At least parts of the Arctic have become like a giant slushie, and that’s a lot easier to melt and melt more quickly.”

Joey Comiso, senior research scientist at Nasa’s Goddard Space Flight Center, said this year’s ice retreat was caused by previous warm years reducing the amount of perennial ice – which is more resistant to melting. It’s created a self-reinforcing trend.

“Unlike 2007, temperatures were not unusually warm in the Arctic this summer. [But] we are losing the thick component of the ice cover,” he said. “And if you lose [that], the ice in the summer becomes very vulnerable.”

Walt Meier, from the National Snow and Ice Data Center that collaborates in the measurements, said: “In the context of what’s happened in the last several years and throughout the satellite record, it’s an indication that the Arctic sea ice cover is fundamentally changing.”

Professor Peter Wadhams, from Cambridge University, told BBC News: “A number of scientists who have actually been working with sea ice measurement had predicted some years ago that the retreat would accelerate and that the summer Arctic would become ice-free by 2015 or 2016.

“I was one of those scientists – and of course bore my share of ridicule for daring to make such an alarmist prediction.”

But Prof Wadhams said the prediction was now coming true, and the ice had become so thin that it would inevitably disappear.

“Measurements from submarines have shown that it has lost at least 40% of its thickness since the 1980s, and if you consider the shrinkage as well it means that the summer ice volume is now only 30% of what it was in the 1980s,” he added.

At this point all we can do is watch, the ice is going to do what its going to do. I’ll try to keep some of the most important graphs posted here and keep up with the most important milestones. For today, what’s stunning to most observers is that we appear to have smashed thru the 4 million square kilometer barrier – The latest value : 3,947,500 km2 according to the Japan Aerospace (JAXA) group. The US NSIDC is somewhere close to that estimate.

For those just beginning to pay attention to the story of ice, NSIDC has a FAQ , and some good primers, here and here.

August 27, 2012

Arctic sea ice appears to have broken the 2007 record daily extent and is now the lowest in the satellite era. With two to three more weeks left in the melt season, sea ice continues to track below 2007 daily extents.

Please note that this is not an announcement of the sea ice minimum extent for 2012. NSIDC will release numbers for the 2012 daily minimum extent when it occurs. A full analysis of the melt season will be published in early October, once monthly data are available for September.